livelock

When two or more processes continuously
change their state in response to changes in the other
process(es) without doing any useful work.

This is similar to deadlock in that no progress is made but
differs in that neither process is blocked or waiting for
anything.

A human example of livelock would be two people who meet
face-to-face in a corridor and each moves aside to let the
other pass, but they end up swaying from side to side without
making any progress because they always move the same way at
the same time.

(this is from The Free On-line Dictionary of Computing)

Previous definition taken from Jargon file is AFAIK
describing the term starvation rather than livelock ... but I'm not the expert ...

A situation in which some critical
stage of a task is unable to finish because its clients perpetually
create more work for it to do after they have been serviced but
before it can clear its queue. Differs from deadlock in that
the process is not blocked or waiting for anything, but has a
virtually infinite amount of work to do and can never catch up.